1. Field of the Invention
The invention relates to an elongate metal body, for instance an aluminium rod with a chosen cross-sectional form manufactured by extrusion.
2. Background Information
Such a body is known in many applications. A well-known application is a skate frame for an ice-skate or roller-skate. Such a frame comprises for instance an elongate carrier manufactured from aluminum by means of extrusion, to which the runner or wheels are connected.
It is a first object of the invention to make an elongate metal body stiffer and stronger without this entailing an increase in weight. In respect of this objective the metal body according to the invention has the feature that the body has at least one cavity extending at least to a considerable degree in longitudinal direction, in which cavity is received a pre-manufactured elongate reinforcing rod, of which at least the ends are coupled to the body in force-transmitting manner.
The embodiment is recommended in which the rod consists substantially of a bundle of longitudinally extending, continuous fibres embedded in a plastic matrix, in particular consisting of carbon, aramid, glass, boron, reinforced polyethylene and other synthetic and ceramic materials. Such a rod of composite material combines a very great longitudinal strength with a low weight.
A very simple and inexpensive embodiment is that in which the rod is connected to the body by glue.
For strengthening and reinforcement this variant can have the special feature that the rod is connected substantially along its whole outer surface to the body.
A further variant is characterized by biasing means for holding the rod under longitudinal bias.
For particular applications this variant can have the special feature that the biasing means are adjustable.
A specific embodiment hereof has the feature that the biasing means comprise screw means.
The biasing means can be embodied such that the rod fits into the cavity with small clearance and the biasing means are adapted to exert a pressure force on the ends of the rod.
An embodiment with optionally adjustable biasing means can have the special feature that the cavity is positioned at a distance from the neutral fibre of the body. The metal body comes under strain of bending due to the longitudinal force exerted at a distance from the neutral fibre. A bending can thus be obtained which, in the case of adjustable biasing means, can be adjusted to a desired value.
This latter embodiment in particular can, as will be described hereinbelow, be important for application in the skating sport. This is the case however for the invention in general. The invention therefore also pertains to a skate frame for an ice-skate or roller-skate which is provided with an elongate metal body having connected thereto an elongate reinforcing rod as specified above.
A runner for an ice-skate is generally ground with a determined radius of curvature. This radius of curvature is arranged in the height direction of the skate.
In the case of short-track skating and 500 meter sprint shaking on the track it is at the moment usual for the skates also to have a certain curvature in sideways direction. The value thereof, which can be expressed in the radius of curvature, is greatly dependent on personal wishes and preferences. At the movement the skate frame is herein usually clamped in a vice, wherein a part of the skate is bent manually. The object of this bending operation is to obtain a better grip on the ice in the bend, whereby the skater can negotiate the bend at an even greater angle and speed without the risk of slipping.
As has been stated, the value of the radius of curvature to be adjusted is very person-dependent. The degree of bending must moreover be adapted to the ice conditions, so that there is a need for an adjustable bending.
For the purpose of grinding the runner it is further desirable that the skate is straight or can be straightened when not in use, so that the runner can be clamped into usual grinding devices. It is therefore desirable that the runner can be straightened again with simple means.
The above described steps according to the invention, for instance biasing means adjustable by means of screw means, obviate the above described problem.
Due to the combination of materials with different coefficients of expansion there occurs a difference in expansion or shrink of the materials in the case of temperature changes. For instance in the combination of an aluminium frame in which a steel runner is arranged, the following phenomenon occurs. A radius in the runner of for instance 20 meters at room temperature will have a radius of curvature at minus 15xc2x0 C. of about 17 meters. This temperature-dependent radius of curvature is undesirable if it does not correspond to the radius of curvature desired at these temperatures. There therefore exists a need to change the effective coefficient of expansion, locally or otherwise, of an aluminum skate frame in order to thus make it possible to compensate for the deformation due to temperature differences.
The stiffness of a skate frame is also of great importance. Due to the great forces during starting, sprinting and taking of a band, the skate and the frame have a tendency to deform. This deformation must be limited to a minimum. If a skate is subjected to bending, a small radius of curvature must be arranged in advance both in height and in sideways direction in order to still have the correct radius of curvature in the bend. This has the disagreeable consequence that the straight part of the skate track must be skated with a small radius of curvature, which adversely affects the speed. For these reasons there therefore exists a need for a stiff skate frame.
This need for more stiffness and strength also exists in other constructions, such as for instance in aluminum boat masts, booms and the like. Other applications relate to ladders, for instance fire ladders, aluminum profiles in the building industry, glasshouse construction etc. Supporting aluminum profiles also often have the limitation of insufficient stiffness and strength. The invention provides a solution herefor.
It is noted that particularly the biasing means according to the invention can cause a bending in two directions. For this purpose two push or pull rods are then connected to the profile, this at mutually differing positions relative to the neutral fibre, for instance such that the one rod causes a sideward bending and the other rod a bending in vertical direction.
By arranging carbon rods in the outer wall of a skate frame the stiffness is improved to a significant extent. Carbon fibres have a stiffness which is a factor 3-6 times higher than that of aluminum, while the specific mass amounts to about half thereof. The strength of carbon is 4-10 times that of aluminum. The structure of the elongate metal body can thus be lighter while retaining strength and stiffness.
Another advantage of carbon fibres is that these fibres display a fully elastic behaviour. This in contrast to for instance the aluminum, where the elasticity limit is relatively low and a permanent plastic deformation occurs quite rapidly when there is load. The stiff and strong carbon fibres prevent this plastic deformation of the aluminum.
The reinforcing rod which according to the invention is added to the elongate metal body has in the most general sense better properties than the material of the metal body itself, particularly in respect of strength and stiffness. The gluing of the rod into the cavity takes place for instance with an epoxy glue. Aluminum bodies are preferably anodized with usual methods to thus obtain a suitable gluing surface. Other cleaning and surface treatments, such as for instance chrome-plating, can be used.
A reinforcing rod can have a desired cross-sectional form, for instance a round form or can have another cross section adapted to the geometry of the cavity or the metal body, for instance square, rectangular, polygonal.
The cavity can for instance be arranged completely internally in the body. A cavity can also be partially open to the outside in longitudinal direction, which simplifies the extrusion process for manufacturing the metal body. The opening of such semi-open forms can be situated on the inside or the outside of the profile. In this latter case the reinforcing rod is partly visible on the outside.
In the case of an enclosed cavity in a metal body a reinforcing rod, which is for instance obtained via a pulltrusion process, is pushed into the cavity. The glue can herein be pre-applied to the rod and/or in the cavity.
Another method is to insert the rod into the cavity without glue. By supplying glue to the one open side and sucking on the other side of the cavity (in which the rod is received), the glue can be applied between the wall of the cavity and the reinforcing rod so that it wholly fills the remaining space.